Only about one in 20 pupils identified as contacts of schoolmates who had Covid-19 went on to test positive, according to a major new study.

Analysis from Public Health Scotland shows 25,507 had at least one positive PCR result during the 2020–21 session. Researchers then examined 1,503 “index case” individuals who had 10 or more school-year pupil contacts.

They found 5.2 per cent of contacts went on to test positive within one to 14 days after exposure to the index case. However, rates increased over the course of the school year as the Alpha and Delta variants emerged.

Significantly, primary schools saw far higher figures than secondaries towards the end of the session, highlighting a possible link between transmission and in-person learning.

READ MORE: When do pupils have to self isolate and what are rules in schools?

While the proportion was similar during the August 17-December 20 term (1.4% versus 1.2%, respectively), a gap opened over the late winter and spring months. In term 3, which covers April 18 to June 25, the pupil contact case rate was 10.5% in primary schools compared with 3.5% among those of secondary age.

Researchers believe the difference could be connected to the phased re-opening of classrooms, which saw P1-7 children return earlier to full-time, face-to-face teaching.

Their report says: “Our findings suggested that pupil contact case rates were similar in term 1 in primary and secondary schools, while this rate was higher in primary schools in term 3.

“Although we were unable to show the specific rates for secondary school pupils for term 2 [February 15-April 1], the reason behind the lower rates in secondary school compared with primary school could be due to primary school pupils spending more time than secondary school pupils in in-person education in schools during this term.

“However, given the variation of in-person learning and mitigations, particularly in term 2, it is impossible to judge the relative significance of these findings or provide a definitive interpretation of the difference between settings.”

HeraldScotland: Tens of thousands of pupils were forced to stay away from school due to self-isolation rules.Tens of thousands of pupils were forced to stay away from school due to self-isolation rules.

The report also stresses that it cannot be established if Covid-19 transmission took place in school settings. It says there could have been additional interaction between index cases and their contacts elsewhere, for example at social events such as playdates or clubs.

The report adds: “It is also possible that contacts had further contact with positive cases during the same period other than their contact with the case, for example other household contacts with Covid—19.” 

Just over 38% of pupils who tested positive for COVID-19 passed the virus on to at least one other pupil.

READ MORE: Greens' door-to-door Covid testing call for Kirkintilloch where half pupils of St Ninian's school are absent

The latest analysis follows the release of figures last week that show a surge in Covid positivity among most school-age year groups.

Willie Rennie MSP, Liberal Democrat education spokesman, warned of the prospect of more “stop-start” education as the Delta variant continues to spread.

“Schools have suffered during the pandemic,” he said.

"Children and young people went through so much turmoil and disruption last year, and that will have a lasting impact on their education experience. With new variants running rampant in both schools and the wider population, there is a real risk that this school year goes a similar way. Schools are effectively having to be shut down already. 

“This can’t be another year of stop-start schooling. Any hope of normality and recovery in education requires the Scottish Government to get a grip on case numbers. Contact tracing should not have been stripped back to just a text message.

"Test and Protect needs to be bolstered, and people need to be properly supported to help get numbers down.” 

HeraldScotland: Liberal Democrat education spokesperson Willie Rennie.Liberal Democrat education spokesperson Willie Rennie.

Recent figures also show self-isolation forced more than 43,000 children and young people to stay away from classrooms for at least two weeks over the 2020-21 session.

Commenting on the last PHS analysis, Jo Bisset, organiser for the UFTScotland campaign group, said: “This proves it was categorically wrong to send home thousands of healthy kids in the last academic year.

“This disrupted their education and ruined their social development. For their parents, it also caused significant stress and anxiety when it came to balancing work and childcare."

She added: “It’s time the Scottish Government stood up to those determined for schools to close and children to fester at home for another year. If they’d taken this stance at this point last year, a whole generation of Scottish children would be in a much better place.”

Education Secretary Shirley-Anne Somerville said: “While it’s encouraging that the vast majority of contacts of a positive case amongst a fellow pupil do not go on to test positive for Covid-19 (via PCR) within 14 days of exposure, we must remain vigilant. We will consider this evidence as we keep the approach to contact tracing and isolation policy amongst school pupils under ongoing review as this term progresses to ensure it is proportionate.”